Recently, a technology of estimating a movement or a movement locus of a vehicle according to wheel speed information for a moving object such as a vehicle having right and left front wheels and right and left rear wheels, with the front wheels designed as steered wheels, has been proposed. For example, a technology of preventing a shift of a movement locus for automatic parking, and a technology of making an amendment for matching between an estimated drive locus and an actual drive locus although a driving condition of a vehicle changes, are well known (refer to patent documents 1 and 2, for example). A technology of geometrically estimating a movement locus of a moving object according to wheel speed information has also been proposed (refer to patent documents 3 through 5, for example).
Patent Document 1: Japanese Laid-open Patent Publication No. 2001-138941
Patent Document 2: Japanese Laid-open Patent Publication No. 2002-362390
Patent Document 3: Japanese Laid-open Patent Publication No. 2011-8385
Patent Document 4: Japanese Laid-open Patent Publication No. 7-81609
Patent Document 5: Japanese Laid-open Patent Publication No. 3-90482